1. Field of the Invention
The present invention relates to a solid-state imaging device such as a CCD linear sensor, a CCD area sensor or the like and a method for driving such a solid-state imaging device.
2. Description of the Related Art
It has been proposed that in a color CCD linear sensor having a plurality of sensor lines be provided with a shutter function by which the amplitudes of a plurality of signals from the sensor lines can be controlled.
A main purpose of such a shutter function is, for example, it use in a color linear sensor having three sensor lines of R(red), G(green) and B(blue), to adjust the white balance of the output voltages from the R, G and B sensors. If the same accumulating time is set, the magnitudes of each of the R, G and B output voltages are different depending on their sensitivities. This leads to the difference of dynamic range in the R, G and B output voltages.
In order to cope with this problem, a correction is performed such that in the latter stage of the signal processes. the output levels are arranged by varying each of the gains of R, G, B and, particularly if a higher quality of an image is required, the output levels of RGB are required to be arranged before the adjustment of gain, namely, just at the CCD output.
Accordingly such a method is used in which if it is assumed that xcfx84ROG is a period from a time when a reading gate pulse is applied to a time when the next reading gate pulse is applied, the xcfx84ROG is set to a charge accumulating period to the sensor portion (this is defined as 1H period), and then an effective accumulating period each of the R,G,B is varied by a shutter pulse input.
A 1H period consists of a period for transferring a signal charge, namely, an effective signal period and the subsequent non-transfer period.
In a prior art, when this effective accumulating period is to be set, the input of the shutter pulse (for example, of making the shutter pulse off) is set in the period other than the effective signal period, namely, the non-effective period. That is, if the effective signal period is set as the input period of the shutter pulse, for example, a potential of a common semi-conductor well area on a semi-conductor substrate side fluctuates as a result of the input of shutter pulse and therefore the wave form of an output signal also fluctuates owing to the influence of the coupling of shutter pulse to affect on the quality of an image. Accordingly, the input time of the shutter pulse is set in a so-called non-transfer period other than the effective signal period.
However, if the input time of the shutter pulse is set in the non-transfer period other than the effective signal period, a variable range of the signal charge accumulating time is so limited that there is no marginal time, because the remaining period the shutter operation becomes is a signal charge accumulating time. Accordingly, if the effective accumulating time is to be set longer, the xcfx84ROG is set as a longer time and the non-transfer period must be made long. At this time, such a drawback is produced that the signal processing time on a set increases.
In view of such aspect, it is an object of the present invention to propose a solid-state imaging device and a method of driving such a solid-state imaging device which enables the shutter operation at anytime in and out of the effective signal period.
According to a first aspect of the present invention, a solid-state imaging device includes a sensor portion for accumulating a signal charge produced by photoelectric conversion, a charge transfer register for transferring the signal charge, a charge/voltage converting portion connected to the charge transfer register, and a means for carrying out a shutter operation for discharging the charge accumulated by the sensor unit in synchronization with a signal charge reset period of the charge/voltage converting portion.
According to a second aspect of the present invention, a method is one of driving a solid-state imaging device having a sensor portion for accumulating a signal charge generated by photoelectric conversion, a charge transfer register, and a charge/voltage converting portion connected to the charge transfer register. The method includes a step of carrying out a shutter operation for discharging a charge accumulated by the sensor portion in synchronization with a reset period of the charge/voltage converting portion.
According to a third aspect of the present invention, a method is one of driving a solid-state imaging device having a plurality of sensor portions and a plurality of sensor lines for accumulating charges generated by photoelectric conversion and a plurality of charge transfer registers for transferring the signal charges and a charge/voltage converting portion connected to the plurality of charge transfer registers. The method includes a step of carrying out a shutter operation for discharging the charges accumulated by the sensor lines in synchronization with a reset period of the charge/voltage converting portion.